Phillips M L, Pullinger C, Kroes I, Kroes J, Hardman D A, Chen G, Curtiss L K, Gutierrez M M, Kane J P, Schumaker V N
Department of Chemistry and Biochemistry, University of California-Los Angeles 90095-1569, USA.
J Lipid Res. 1997 Jun;38(6):1170-7.
Individuals homozygous for the e2 allele encoding apolipoprotein E exhibit a remnant removal defect and accumulate substantial levels of intestinally derived particles containing apolipoprotein B-48 (apoB-48). Such lipoproteins were isolated from the plasma of E2/E2 individuals, and further purified by affinity chromatography using a polyclonal antibody specific for selective binding and removal of apoB-100-containing lipoproteins. The unbound lipoproteins, termed chylomicron remnants, were particles with average hydrated diameters of 31.2 nm as determined by dynamic light scattering. They contained apoB-48 and ApoE as their only protein components. The number of apoB-48 molecules on each lipoprotein was assessed by counting the number of antibody molecules bound to the surface of the chylomicron remnants, using either a monoclonal antibody specific for a single epitope on apoB-48 or a mixture of two such monoclonal antibodies specific for widely separated epitopes. The results of this analysis seem unambiguous: no more than one apoB-48 resides on the chylomicron remnant. Because apoB appears to be unable to transfer among lipoprotein particles, it may be inferred that nascent chylomicrons also contain a single copy of apoB-48.
编码载脂蛋白E的e2等位基因纯合个体表现出残余物清除缺陷，并积累大量含有载脂蛋白B-48（apoB-48）的肠道来源颗粒。从E2/E2个体的血浆中分离出此类脂蛋白，并使用对选择性结合和去除含apoB-100的脂蛋白具有特异性的多克隆抗体，通过亲和色谱进一步纯化。未结合的脂蛋白，称为乳糜微粒残余物，通过动态光散射测定，其平均水合直径为31.2 nm。它们仅含有apoB-48和载脂蛋白E作为蛋白质成分。通过使用对apoB-48上单个表位具有特异性的单克隆抗体或对广泛分离的表位具有特异性的两种此类单克隆抗体的混合物，通过计数与乳糜微粒残余物表面结合的抗体分子数量，评估每个脂蛋白上apoB-48分子的数量。该分析结果似乎明确无误：乳糜微粒残余物上存在不超过一个apoB-48。由于apoB似乎无法在脂蛋白颗粒之间转移，因此可以推断新生乳糜微粒也含有单个拷贝的apoB-48。
